This wilt disease is caused by a soil-inhabiting fungus (Fusarium oxysporum lycopersici) that infects only tomatoes. The fungus persists indefinitely on plant debris or in the soil. Fusarium is more prevalent in warm-weather areas. The disease is spread by contaminated soil, seeds, plants, and equipment. The fungus enters the plant through the roots and spreads up into the stems and leaves through the water-conducting vessels in the stems. These vessels become discolored and plugged. This plugging cuts off the flow of water and nutrients to the leaves, causing leaf yellowing and wilting. Affected plants may or may not produce fruit. Fruit that is produced is usually deformed and tasteless. Many plants will die. For more information about fusarium wilt, see Verticillium or Fusarium Wilt.
No chemical control is available. Destroy infected plants promptly. Fusarium can be removed from the soil only by fumigation techniques. (For more information on soil fumigation, see Soil Fumigation and Solarization.) However, the best solution is usually to use plants that are resistant to fusarium wilt. This is denoted by the letter "F" after the tomato variety name. For a list of wilt-resistant varieties, see Disease Resistance of Tomatoes.
Plant Care for Tomatoes